More useful error when parser isn't supported

[lindsayplatt]

If you use result(job) with the FeatureCoverageOPeNDAPIntersectionAlgorithm algorithm, you get an error about the parser not being supported. This is useful but might lead people to believe that they cannot use that algorithm at all. Perhaps adding what they can do instead would be useful:

Original error

Error: parser for FeatureCoverageOPeNDAPIntersectionAlgorithm not currently supported.

Suggested error:

Error: parser for FeatureCoverageOPeNDAPIntersectionAlgorithm not currently supported. Retrieve your results using `geoknife::download()` and then parsing the results yourself.